Abstract
The light-induced degradation of dichloroacetic acid in aqueous suspensions containing the TiO2 photocatalyst Hombikat UV 100 was investigated. The reactions were performed in a black body reactor in which the rate of conversion, defined as the time derivative of the extent of conversion, is not affected by the light scattering properties of the photocatalysts. At sufficiently high concentrations of both the probe compound and the photocatalyst the rate of conversion was found to be unswayed by the initial concentration of the probe compound, the mass concentration of the photocatalyst, and the suspension volume. Thus, the chosen experimental conditions enable the determination of the rate of conversion and the quantum yield of the light induced degradation of dichloroacetic acid in aqueous photocatalyst suspension with sufficiently good reproducibility. The experimental procedure employed here seems to be generally applicable to determine rates of conversion and quantum yields that possibly allow a comparison of the activities of photocatalysts in aqueous suspensions.
Highlights
Heterogeneous photocatalysis in solid–liquid systems is considered as an effective method to harvest photons for the oxidative degradation of organic water pollutants, the generation of molecular hydrogen by water splitting or reforming of organic compounds, the fixation of carbon dioxide or molecular nitrogen, and the synthesis of organic compounds
The experimental results presented above clearly evince that the rate of a photocatalytic reaction in suspension can be determined unaffected by the scattering properties of the photocatalyst when a black body photoreactor is employed
It was shown that experimental conditions can be achieved under which the rate of the photocatalytic degradation reaction, defined as the time derivative of the extent of reaction, is constant within the limits of experimental error
Summary
Heterogeneous photocatalysis in solid–liquid systems is considered as an effective method to harvest photons for the oxidative degradation of organic water pollutants, the generation of molecular hydrogen by water splitting or reforming of organic compounds, the fixation of carbon dioxide or molecular nitrogen, and the synthesis of organic compounds. New photocatalysts and photocatalytically active composites are being synthesized and investigated with respect to possible applications in heterogeneous photocatalysis [1,2,3,4,5,6,7,8]. It is crucial that the photocatalytically active solid is stable under the conditions of the desired light-induced chemical reaction, and that it has a high photocatalytic activity. The latter condition inevitably requires the comparative assessment of the activities of semiconductors and composites intended as photocatalysts. Several methods have been proposed for this comparative assessment of photocatalytic activities in suspensions. The reaction rate at which a probe compound is photocatalytically converted, is used as the measure of the photocatalytic activity of the solid under consideration
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